1. Field of the Invention
The present invention relates to an optical apparatus including an optical element utilizing electro-wetting (electro-capillarity), and in particular to power supply means for driving the element.
2. Related Background Art
Of optical systems built into optical apparatuses such as a still camera and a video camera, those capable of changing a focal length mostly change a focal length of the entire optical system by mechanically moving part of lenses (or a lens group) comprising the optical system in a direction of an optical axis.
For instance, Japanese Patent No. 2633079 shows a configuration wherein, of a zoom lens-barrel comprising a first group of lenses moving in a direction of an optical axis by zooming, a first group of lens-barrels moving in the optical axis direction on movement of the first group of lenses and a cam barrel moving in the optical axis direction due to movement of the first group of lens-barrels, the first group of lens-barrels fit an outer-diameter side of a fixed barrel, the cam barrel fits an inner-diameter side of the fixed barrel, and a front part of the cam barrel fits an inner diameter side of the first group of lens-barrels, and the cam barrel is moved in the optical axis direction so as to move the first group of lenses and perform zooming.
Thus, in the case of changing a focal length by mechanically moving lenses (or a lens group) in a direction of an optical axis, there is a deficiency, that is, complicated mechanical structure of the optical apparatus.
To solve this deficiency, there is a case of rendering a focal length variable by changing optical characteristics of a lens itself.
For instance, Japanese Patent Application Laid-Open No. 8-114703 provides a varifocal lens wherein, in the case where hydraulic fluid is filled in a pressure chamber at least one side of which is comprised of a transparent elastic diaphragm, and the transparent elastic diaphragm is deformed by hydraulic fluid pressure exerted on the diaphragm to render a focal length under variable control, the deformed form of the transparent elastic diaphragm is optimized so as to make lens aberration less likely to occur, and also hydraulic fluid pressure in the pressure chamber is measured with a pressure sensor formed on the transparent elastic diaphragm so that, by adjusting hydraulic fluid pressure based on that value, change of a focal length due to thermal expansion and contraction of hydraulic fluid and so on can also be controlled.
In addition, in Japanese Patent Application Laid-Open No. 11-133210, an electric potential difference is given between a first electrode and a conductive elastic plate to lessen the space between them by generating attraction by Coulomb's force, and it consequently becomes possible, by using a volume of transparent liquid excluded from the space between them, to make convex and deform a central portion of the transparent elastic plate with respect to its back facing the transparent liquid. Then, a convex lens is formed by the convex-deformed transparent elastic plate, transparent plate and the transparent liquid filled between them, so that power of this convex lens is adjusted by the above electric potential difference to constitute a varifocal lens.
On the other hand, a varifocal lens using electro-capillarity is disclosed by WO99/18456. If this technique is used, electrical energy can be used directly to change form of a lens formed by an interface between the first and second liquid, so that it becomes possible to make the lens varifocal without mechanically moving it.
However, the above-mentioned related arts have the following problems. For instance, the above Japanese Patent Application Laid-Open No. 8-114703 describes an actuator controlling apparatus for driving an actuator wherein, as the actuator, a unimorph mechanism by a piezoelectric element formed on a transparent elastic diaphragm is utilized. However, this known technique requires high rigidity of the elastic deformed portion, and consequently has a fault of requiring large amounts of electric power.
Moreover, the above Japanese Patent Application Laid-Open No. 11-133210 also requires high rigidity of the elastic deformed portion, and consequently has a fault of requiring large amounts of electric power likewise.
Furthermore, the above WO99/18456 can change optical power with small amounts of electric power since there is no mechanical movable part, but there is no detailed description of power means, and a technique for controlling optical power with precision and small amounts of electric power is not disclosed.